Method of preventing knot breakage during drawing of yarn



Jan. 16, 1968 M. F. cuLPaN 3,

METHOD OF PREVENTING KNOT BREAKAGE DURING DRAWING OF YARN Filed April13, 1964 2 Sheets-Sheet 1 Inventor M c/Ma ib uzl/L Pm QZZ W M A ttorney;

M. F. QULFIN Jan, 1%, E%$

METHOD OF PREVENTING KNOT BREAKAGE DURING DRAWING OF YARN 2 Sheets-Sheet2 Filed April 13, 1964 United States Patent ()fitice gfidig i PatentedJan. 16, 1968 3,364,293 IWETHGD F PREVENTING KNOT BREAKAGE DURINGDRAWING OF YARN Michael Frank Culpin, Pontypool, England, assignor toBritish Nylon Spinners Limited, Pontypool, England Filed Apr. 13, 1964,Ser. No. 359,106 Claims priority, application Great Britain, Apr. 24,1963, 16,992/ 63 3 Claims. (1. 264-490) ABSTRACT OF THE DISQLGSUREMethod and apparatus for suddenly releasing the tension in a syntheticyarn which is being drawn so that the presence of a knot in the yarnwill not increase the tension in the drawing zone to a value at whichthe yarn will break. The tension release device is one which slowlylengthens the yarn path between feed rolls and a snubbing pin prior tothe approach of a knot and which then suddenly releases the yarn reservejust before the knot reaches the drawing zone. The tension releasedevice may be any of several known devices and may be operatedautomatically or manually.

Disclosure This invention relates to drawing machines for the permanentstretching or drawing in the solid state of synthetic yarn and moreparticularly to such machines as are capable of handling knotted yarn.

The word yarn as used in this specification is to be understood asincluding both monoiilamentous yarn (i.e. a monofilament) andmultifilamentous yarn.

It is well-known to draw synthetic yarn in the solid state in order toincrease its strength, which may be measured by the tenacity in gramsper denier at break. The drawing is commonly effected by passing theyarn around (a) a feed roll and (b) a draw roll revolving at a greaterperipheral speed than the feed roll. The single feed and draw rolls mayeach be substituted by multiple rolls to ensure that the yarn isadequately gripped, alternatively nip rolls maybe employed. The tendencyof the yarn to slip on the roll may also be countered by winding theyarn several times around the roll, conveniently with the use of anauxiliary roll to separate the turns, known as a separator roll. Indrawing yarn consisting of synthetic filaments, for example, syntheticlinear polyamide filaments such as polyhexamethylene adipamide ones, theseat of the drawing action may be advantageously localised by theemployment of a snubbing pin situated between the feed roll (or rolls)and the draw roll (or rolls), round which pin the filaments are loopedon their way from the feed roll to the draw roll. In this case nearlyall the drawing of the yarn occurs at the said snub'oing pin, that is tosay, very close thereto or actually thereon.

However, owing to the use of bobbins and for other practical reasons,undrawn yarn cannot be made commercially in indefinite long lengths, andconsequently it has to be knotted occasionally when a new length isjoined on to the old one. Trouble is then apt to be experienced,especially in the case of the heavier deniers e.g. a multifilament yarnof 800 denier or over, when the knot arrives at the drawing point orzone, owing the rupture taking place. The reason for the rupture is thatthe knot itself is difiicult or impossible to draw by reason of itsincreased denier and the physical changes in the filaments brought aboutby the operation of knotting. Particular difficulty is encountered whenyarn of relatively high tenacity is to be manufactured because in thiscase the filaments are drawn at a draw ratio near to the maximumpossible draw ratio.

It has now been found possible temporarily to suppress the drawingaction of a conventional machine while a knot passes through and thusprevent rupture of the filaments. The temporary suppression of thedrawing is accomplished by slowly lengthening the yarn path between thefeed roll and the snubbing pin with conventional mechanical means priorto the approach of the knot, so that a reserve of yarn accumulates. Thisyarn is suddenly allowed to return to its shorter path (i.e. the pathbefore lengthening) by the aforesaid conventional mechanical means justbefore the knot reaches the drawing zone. This causes a sudden releaseof the reserve of yarn, thereby depressing the tension nearly to zeroand in any case far below the drawing tension so that there is notendency for drawing of the knot to occur. It is important that theaforesaid lengthening of the yarn path be sutficiently slow for thedrawing process to be unaffected or not noticeably affected. The drawingzone is in the immediate neighbourhood of the snubbing pin being for themost part actually on it and/or adjacent thereto.

Accordingly the invention consists as already indicated, of a processfor drawing in the solid state synthetic yarn with occasional knottedjoints comprising forwarding said yarn from one or more conventionalfeed rolls to one of more conventional draw rolls revolving at a greaterperipheral speed than said feed rolls, the yarn passing round a snubbingpin on its way from the feed rolls to the draw rolls, slowly lengtheningthe yarn path between the feed rolls and the snu-bbing pin byconventional mechanical means prior to the approach of a knot and by thesame means suddenly releasing the reserve of yarn thus accumulated byallowing the yarn to return to its original unlengthened path justbefore the knot reaches the drawing zone.

Apart from polyamides, already mentioned, examples of other syntheticfilaments to which the present process applies are:

stereospecific polypropylene polyethylene terephthalatepolyacrylonitn'le polyethylene The invention includes synthetic yarnswhenever drawn by the above process.

The knotted joint may be made in the synthetic yarn by numerous knownprocesses. A most convenient way of knotting is described in BritishPatent No. 956,992. A knot made in this manner in a multifilament yarnof say, 800 denier, might occupy a length of yarn of about 2 inches.

Numerous forms of apparatus which may be used to lengthen the path ofthe yarn are illustrated by way of example in the accompanyingdiagrammatic drawings whereof descriptions are subjoined. In all thedrawings the broken line shows the original (unlengthened) path of theyarn and the full line the lengthened path thereof. The pulleys shown inthe drawings are all idler pulleys; in other words they merely serve asyarn guides.

FIGURE 1 illustrates a device comprising a disc 1 rotatable about itscentre 2 and bearing two idler pulleys 3, 4. The yarn is led to and fromthe said disc by the idler pulleys 5, 6 respectively. The yarn path islengthened by rotating the disc for a fraction of a turn in a clockwisedirection. On allowing the disc suddenly to turn back in ananti-clockwise direction until the yarn assumes the shortened path shownby the broken line 7, the drawing action is temporarily suppressed.

FIGURE 2 shows a device comprising a plunger 7 bearing an idler pulley8. When the plunger is raised the yarn path between the idler pulleys 9,10 is lengthened.

FIGURE 3 depicts a device similar to that of FIG- URE 2, except that atriple plunger 11 bearing 3 idler 3 pulleys 12, 1.3, 14 is incorporated,the yarn path being controlled by the aforesaid three pulleys inconjunction with the idler pulleys 15, 16, 1'7, 18.

FIGURE 4 is a diagram of a device somewhat analogous to agate tensioner,wherein the yarn path is lengthened by increasing the distance betweenthe fixed idler pulleys 19, 29, 21 and the pulleys 22, 23 which aremounted on an arm which pivots at 24.

FIGURE pictures a device comprising a peripherally grooved disc 25eccentrically pivoted at 26 and idler pulleys 27, 28 for guiding theyarn. The path of the yarn which slides over the disc 25 in theperipheral groove, is lengthened and shortened by turning the aforesaiddisc 25. Preferably the latter is furnished with a periphery capable ofrevolving as the yarn passes thereover in order to eliminate anyfriction caused by the yarn sliding over the motionless disc. 7

FIGURE 6'portrays a truncated cone 29 mounted on a spindle 30 capable ofbeing shifted axially in its bearings 31, 32. The yarn guided by thepulleys 33, 34 passes round the cone. By shifting the cone so that theyarn passes round a larger or smaller circumference thereof the yarnpath can be lengthened or shortened.

Whilst it is sometimes convenient to operate the mechanical means forlengthening and shortening the yarn path manually, the device may berendered automatically operable by the employment of conventionalelectronic means and/ or electrical relays in conjunction with knownmeans for detecting and signalling the approach of the knot. For thelatter purpose devices incorporating the principles of the numerousknown slub catchers can be applied.

The following example is for the purpose of illustrating not restrictingthe invention.

EXAMPLE A tow of total denier 6400 consisting of 8 yarns each containing200 filaments of 4 denier is drawn at an effective draw ratio of 5. Eachof the 8 yarns is knotted at different places in the tow by the methoddescribed in British Patent No. 956,992. Each knot extends over 2 inchesof the yarn. The knots occur in each yarn once every 100,000 feetapproximately. The tow passes through the feed rolls at 100 feet perminute, then round the snubbing pin and finally through the draw rollsat 500 feet per minute. 500 feet per minute is equivalent to five sixthsof a foot, i.e. inches, in one tenth of a second. This is a suitabletirne to suppress the drawing action in order to permit the passage of aknot, because a length of yarn of 10 inches allows for the knot itself(2 inches) for some yarn on either side thereof, of which the propertiesmay have been adversely affected in the process of knotting and also forsome slight inaccuracy in timing the release of the yarn reserve inorder to suppress the drawing action. During seconds before a lmot inone of the 8 yarns is due to arrive at the snubbing pin the reserve of10 inches in the yarn is slowly accumulated by means of the apparatusshown in FIGURE 2 which is placed between the feed rolls and thesnubbing pin. The time taken to lengthen the yarn path by 10 inches isthus 20 seconds. The reserve of yarn is released just before the knotreaches the snubbing pin. No rupture of the yarn occurs. This operationdoes not affect the drawing of the other 7 yarns which proceed normallyuntil the arrival of a knot is imminent in another of the 8 yarns.Separate devices for each yarn can be provided but it is more convenientto employ one device capable of being shifted under the particular yarnthe path of which is required to be lengthened, for it is to beunderstood that during the process of drawing and passage round thesnubbing pin, all 8 yarns comprising the tow are in practice spread outside by side in ribbon formation.

What I claim is:

1. A process for drawing in the solid state synthetic yarn havingoccasional knotted joints comprising forwarding said yarn fromconventional feed roll means to conventional draw roll means whichrevolve at a greater peripheral speed than said feed roll means, theyarn passing round a snubbing pin on its way from the feed roll means tothe draw roll means, slowly lengthening the yarn path between said feedroll means and the snubbing pin by conventional mechanical means priorto the approach of a knot and by the same means suddenly releasing thereserve of yarn thus accumulated by allowing the yarn to return to itsoriginal unlengthened path just before the knot reaches the drawingzone.

2. A process for drawing inthe solid state polyhexamethylene adipamideyarn of a denier of at least 800 having occasional knotted jointscomprising forwarding said yarn from conventional feed roll means toconventional draw roll means which revolve at a greater peripheral speedthan said feed roll means, the yarn passing round a snubbing pin on itsway from the feed roll means to the draw roll means, slowly lengtheningthe yarn path between said feed roll means and the snubbing pin byconventional mechanical means prior to the approach of a knot and by thesame means suddenly releasing the reserve of yarn thus accumulated byallowing the yarn to return to its original unlengthened path justbefore the knot reaches the drawing zone.

3. A process as in claim 2 wherein the step of lengthening the yarn pathbetween thefeed roll means and the snubbing pin is carried out so slowlyas to have substantially no effect on the drawing process and whereinthe step of suddenly releasing the reserve of yarn depresses the tensionin the yarn to a value at which there is substantially no tendency fordrawing of the knot.

References Cited UNITED STATES PATENTS 2,847,703 8/1959 Schrenk et al.264167 2,930,102 3/1960 Hitch-in et al. 28-71.3 2,990,603 7/1961 Keith2871.3

ALEXANDER H. BRODMERKEL, Primary Examiner.

A. K. KOECKERT, Assistant Examiner.

